Fiber Reinforced Superalloys

Abstract

(TFRS) a r e t h e f i r s t o f a f a m i l y of h i g h temperature composites t h a t o f f e r t h e p o t e n t i a l f o r s i g n i f i c a n t l y r a i s i n g h o t component o p e r a t i n g temperatures and t h u s l e a d i n g t o improved h e a t engine performance. Thls s t a t u s r e v i e w o f TFRS r e s e a r c h emphas i z e s t h e p r o m i s l n g p r o p e r t y d a t a developed t o d a t e , t h e s t a t u s o f TFRS comp o s i t e a i r f o i l f a b r i c a t i o n technology, and t h e areas r e q u i r i n g more a t t e n t i o n t o a s s u r e t h e i r a p p l i c a b i l i t y t o h o t s e c t i o n componentsThe object o f this paper is to revlew t h e development of fiber reinforced superalloys. First refractory metal fiber and matrlx alloy development wlll be reviewed. This will be followed by a discussion of fabrication techniques 2 f o r TFRS and p r o p e r t y r e s u l t s of importance f o r t h e i r use a t h i g h temperatures.Component f a b r i c a t i o n and f a b r i c a t i o n c o s t d a t a f o r a s p e c i f i c TFRS system w i l l t h e n be discussed i n t h e f i n a l s e c t i o n . I. FIBER DEVELOPMENTR e f r a c t o r y m e t a l w i r e s have received a g r e a t d e a l o f a t t e n t i o n as f i b e r r e i n f o r c e m e n t m a t e r i a l s f o r h i g h use temperature composites i n s p i t e o f t h e i r poor o x i d a t i o n r e s i s t a n c e and h i g h d e n s i t y . When used t o r e i n f o r c e a d u c t i l e and o x i d a t i o n r e s i s t a n t m a t r i x , t h e y are p r o t e c t e d f r o m o x i d a t i o n and t h e i r s p e c i f i c s t r e n g t h I s much h i g h e r t h a n t h a t o f s u p e r a l l o y s a t e l e v a t e d temperat u r e s . The m a j o r i t y o f t h e s t u d i e s conducted on r e f r a c t o r y w i r e / s u p e r a l l o y composites have used t u n g s t e n o r molybdenum w i r e , a v a i l a b l e as lamp f i l a m e n t o r thermocouple w i r e , as t h e r e i n f o r c e m e n t m a t e r i a l . These r e f r a c t o r y a l l o y s were n o t designed f o r use i n composites n o r f o r optimum mechanical p r o p e r t i e s i n t h e temperature range o f i n t e r e s t f o r h e a t engine a p p l i c a t i o n , 1000 t o 1200 O C (1830 t o 2190 OF).Lamp-filament w i r e such as 218CS t u n g s t e n was most e x t e ns i v e l y used i n e a r l y s t u d i e s . The s t r e s s -r u p t u r e p r o p e r t i e s o f 218CS t u n g s t e n w i r e were s u p e r i o r t o t h o s e o f r o d and b u l k forms o f t u n g s t e n and showed prom- Table I . The above approach p r e c l u d e d development o f new a l l o y s s p e c i f i c a l l y designed f o r s t r e n g t h a t t h e i n t e n d e d composlte use temperatures. The s t r e s s -r u p t u r e and t e n s i l e p r o p e r t i e s determined f o r t h e w i r e s developed a r e summarized i n Table I 1 E x c e l l e n t p r o g r e s s was made i n p r o v i d i n g w i r e s w i t h i n c r...